To provide the consumers with a safe and pleasing surroundings, the Ministry of Economic Affairs (MOEA) set a policy for small business, which is called Good Store Practice (GSP), in July 1995. Since September 1996, the MOEA began to accept the applications. The goal of the study is to make use the zone of tolerance theory, and to analyze the effect of the GSP system on the service quality of the restaurant. The survey was conducted in a western-style chain restaurant, which is also a member of the GSP. From the outcome of the research, people who have never heard of the GSP system are of high 44.2%. It shows that customers generally lack of recognition of the system. The publicity of the mass media leaves a lot to be desired. The cleanness of toilet is a major service quality problem. The manager should improve on-job training for staffs to maintain the sanitation quality of the restaurant. The outcome also shows that the zone of tolerance model is very effective in evaluating service quality.